Instruction 01-prowlarr-flow: Reading

Scope and legal boundary

Prowlarr manages indexer definitions and makes search results available to compatible applications. This course covers architecture, configuration control, and testing. Use only indexers and content sources you are authorized to use.

End-to-end architecture

flowchart TD
    U["User"] --> R["Seerr"]
    R --> A["Sonarr / Radarr"]
    A --> P["Prowlarr"]
    P --> I["Authorized indexer"]
    A --> D["Download client"]
    D --> C["Completed download"]
    A --> M["Import + rename"]
    M --> L["Plex / Jellyfin"]

Prowlarr does not replace Sonarr or Radarr. Sonarr/Radarr own the monitored title, quality policy, candidate evaluation, download handoff, and completed-download import. Prowlarr centralizes indexer connectivity and synchronization.

Service contracts before clicking

Record the following for Prowlarr, Sonarr, Radarr, and each download client:

• Docker service name and internal port.
• LAN address only if humans need it.
• Docker network.
• API credential owner and rotation plan.
• Download category.
• Root folder and container path mappings.
• Health/test button expected result.

Within one Compose network, prefer service DNS names such as http://sonarr:8989. From Prowlarr's container, localhost:8989 points back to Prowlarr and is wrong unless both processes genuinely share a network namespace.

Applications and synchronization

Adding Sonarr/Radarr to Prowlarr creates an application relationship. The exact sync settings can vary, but the intended result is clear: indexers approved for a target application appear there with the proper categories and settings.

Treat the connection test and the synchronization test as different requirements:

1. Connection: Can Prowlarr authenticate to the target API?
2. Synchronization: Does the desired indexer configuration actually appear and remain consistent?

Indexer tests

An indexer test can fail at several layers:

DNS -> TCP/TLS -> provider response -> authentication -> rate limit -> categories -> application policy

Do not regenerate every API key because DNS failed. Capture the exact test time, response class, and one hypothesis.

Download handoff and categories

Sonarr/Radarr normally send a selected release to the download client. Categories keep traffic separated, for example tv and movies. The client must report completed paths that the ARR container can resolve.

The most reliable beginner layout gives download client and importers a consistent /data view:

Host: /srv/data                 Containers: /data
  /torrents                       /torrents
  /usenet                         /usenet
  /media/tv                       /media/tv
  /media/movies                   /media/movies

This reduces remote-path mappings and enables hardlinks when source and destination are on the same filesystem.

Hardlinks

A hardlink gives two directory entries to the same underlying file data. It avoids a second full copy while allowing the downloader to seed from one path and the media library to use another.

Conditions include:

• Same filesystem/device.
• Compatible permissions.
• Application configured to use hardlinks where appropriate.
• Paths presented consistently.

On Linux, compare device and inode values with stat. Two paths with the same device and inode refer to the same file data.

1. Open the Lesson for prior-knowledge check, guided practice, and required Feynman teach-back.
2. Then complete Lab, Homework, and Quiz for this topic.